Junior ADU (JADU): What It Is and What the Rules Require
A junior ADU, or JADU, is an accessory dwelling unit of up to 500 square feet created entirely within the walls of your existing single family home. It must have its own exterior entrance and an efficiency kitchen. It may share a bathroom with the main house.
California requires the owner to live in either the main house or the JADU. Woollard Construction builds them across the Temecula Valley. License B-842038. Call (951) 551-6165.
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Junior ADU Rules in California
The requirements differ from a standard ADU in ways that matter.
500 square feet.
Entirely within the existing walls of the single family home. A JADU cannot be a new detached structure.
A separate exterior entrance is required.
An efficiency kitchen is required. The requirements are lighter than a full ADU kitchen, and a full size range is not needed.
A JADU may share a bathroom with the main house, which no other ADU type allows.
Required. You must live in either the main house or the JADU. This is the biggest difference from a standard ADU, where the requirement was removed for units permitted after January 1, 2020.
No additional parking required.
A decision on a complete application within 60 days.
You are allowed one JADU in addition to one standard ADU on nearly every single family lot in California.
Junior ADU vs Standard ADU
Size
500 square feet versus up to 1,200. A JADU is a converted bedroom or a section of the house, not a residence in its own right.
Owner occupancy
The decisive difference. A standard ADU carries no owner occupancy requirement. A JADU does. If your plan is to rent out the whole property and live elsewhere, a JADU will not work.
Cost
A JADU is the least expensive path to a legal second unit after a garage conversion, because there is no foundation, no roof, and no new exterior walls. You are adding an entrance, an efficiency kitchen, and separation.
Bathroom sharing
Only a JADU can share a bathroom with the main house. In practice most owners add one anyway, since a shared bathroom sharply limits who will rent it.
Speed
The lightest permit path of any option, and the least exterior change, which means the lightest HOA architectural review.
When a Junior ADU Is the Right Choice
Your lot has no room for anything else
Measure four feet from your rear and side property lines and ten feet from the house. If the remaining rectangle cannot hold a detached unit, and you have no garage to convert or want to keep it, the space inside your house is what remains.
You want to build both
A JADU plus a standard ADU on the same lot is permitted. Some owners convert a bedroom into a JADU now and build a detached unit later as budget allows.
You are housing family
A JADU suits an adult child, a parent who wants proximity rather than full separation, or a live in caregiver. The owner occupancy requirement is irrelevant when you are living there anyway.
You need the fastest legal route
Less permitting, less construction, less exterior change. A JADU finishes in a fraction of the time a detached build takes.
Which Room Becomes the JADU
Most homeowners already have the space. Finding it is a floor plan question, not a construction question.
A bedroom on an exterior corner
The ideal candidate. Two exterior walls give you options for the required entrance, and a corner room can be separated from the rest of the house with a single door. Most JADUs we build start here.
A room adjacent to an existing bathroom
Plumbing distance is the single biggest cost variable. A bedroom sharing a wall with a bathroom means short runs for the efficiency kitchen sink and any new fixtures. A room on the opposite corner of the house means opening floors or walls to reach it.
A converted den, office, or bonus room
Often better than giving up a bedroom, because the main house keeps its bedroom count for resale. A bonus room over a garage can work where it has exterior wall access for the entrance.
The 500 square foot ceiling
A JADU cannot exceed 500 square feet. Most single bedrooms run 120 to 200 square feet, so a single bedroom conversion sits well under the cap. Combining a bedroom with an adjoining den or bath gets you closer to it, and that is usually the more rentable configuration.
What to check yourself before calling. Walk your floor plan and ask three questions. Which rooms have an exterior wall where a door could go. Which rooms sit near existing plumbing. Which room could your household actually give up. If one room answers all three, you have a JADU candidate.
What a Junior ADU Costs
For comparison, our detached new build units run $225,000 at 499 square feet and $290,000 at 749 square feet, covering construction, plans, engineering, typical utilities, and standard finishes. A JADU costs a fraction of that, because the structure already exists. See the full cost breakdown.
What moves a JADU price
Whether you add a bathroom or share the existing one. How far the space sits from existing plumbing, since a new kitchen sink and bathroom need supply and drain lines run to them. Whether a new exterior door requires structural framing or fits an existing opening. Panel capacity for the added kitchen circuits. Sound separation between the JADU and the main house.
What is excluded from any base number
Site plan, city permit fees, school fees, and engineering consultants where required.
What the Work Involves
Creating the separate entrance
A JADU needs its own exterior door. Where an existing window or slider can be converted, the cost stays low. Where a new opening has to be cut into a load bearing wall, that means a header, engineering, and inspection.
Building the efficiency kitchen
Cabinets, a sink, cooking facilities, and counter space. California's efficiency kitchen standard is lighter than a full ADU kitchen. The real work is running supply and drain lines to a spot in your house that never had them.
Separating the JADU from the house
An interior connecting door is permitted, and many owners keep one. Where the unit will be rented to someone outside the family, we recommend proper sound separation and a lockable door.
Handling the plumbing
This is the variable. A converted bedroom next to an existing bathroom is a straightforward tie-in. A bedroom on the far corner of the house means opening floor or walls to run new lines.
Where We Build Junior ADUs
JADUs are particularly useful in the dense tract neighborhoods where nothing else fits. Harveston, Wolf Creek, Redhawk, and Morgan Hill in Temecula. Gated communities like Bear Creek and Roripaugh Ranch, where minimal exterior change means the lightest architectural review.
On Wine Country septic properties, a JADU sometimes avoids a septic upgrade entirely, because the county evaluates the added load differently than it does a full second dwelling.
Licensing and Credentials
California general contractor license
B-842038, active and in good standing.
Experience
Spencer has worked in construction since 1990 and has built in the Temecula Valley since 2004. More than 350 completed projects.
Bonded and insured
General liability and workers compensation certificates provided before work starts.
Licensed subcontractors only
Every subcontractor on your job is licensed and insured.
Verify any California contractor license, including ours, through the Contractors State License Board. Check it before you hire anyone.
What Temecula Valley homeowners say
More than 350 completed projects in Southern California and the Temecula Valley, and a five star rating across Google, Yelp and Houzz.
“Everything about our experience with Woollard Construction was amazing!! Spencer was fantastic!! He was punctual, professional and great at communicating where we were in every step of the process. Our ADU is beautiful and we are so happy with how everything turned out.”
“The bid was competitive and very reasonable. Spencer was responsive and accommodating; always ready to answer any questions that came up or think outside the box to keep us on budget. His subcontractors were professional and efficiently organized. The whole process was extremely quick once the permits were in place... just under four months from start to finish.”
A junior ADU is a unit of up to 500 square feet created within the existing walls of a single family home, with its own exterior entrance and an efficiency kitchen. It may share a bathroom with the main house.
A JADU is capped at 500 square feet, must be inside your existing home, may share a bathroom, and requires the owner to live on the property. A standard ADU can be up to 1,200 square feet, can be detached, needs its own bathroom, and has no owner occupancy requirement.
Yes. California requires the owner to occupy either the main house or the JADU. This requirement was not removed the way it was for standard ADUs.
Yes. State law allows one standard ADU and one junior ADU on nearly every single family lot.
No. A JADU may share a bathroom with the main house. Most owners add one anyway, since a shared bathroom limits who will rent the unit.
Usually comparable, and it depends on the plumbing distance. A JADU next to an existing bathroom is very cheap. A JADU on the far side of the house can cost more than converting a garage.
Get a free consultation.
We walk your floor plan, find the space that works, and tell you what a junior ADU would cost in your home. Call (951) 551-6165 or request a site visit online.